Micromaser with Stationary Non-Poissonian Pumping

Ulrike Herzog, János A. Bergou

Yu. M. Golubev

Ulrike Herzog

The model commonly used to describe non-Poissonian pumping of micrornasers refers to periodic pumping where the possible arrival times of the pump atoms are separated by constant time intervals.1 In contrast to this, we study a micromaser with strictly stationary pumping.2 We investigate the level-selective statistics of the atoms leaving the cavity as well as the photon statistics of the cavity field. Our method is based on treating the statistics of the arrival times of the individual pump atoms, which are in the upper state of the microwave transition, with the help of the theory of stochastic point processes.

István Németh

Ulrike Herzog

A method is presented for theoretically investigating the properties of a one-atom micromaser with stationary non-Poissonian pumping. The method is based on treating the statistics of the arrival times of the individual pump atoms with the help of the theory of stochastic point processes. Considerable simplification is achieved by assuming the pump statistics to be described by a stationary renewal process. Thus the influence of super- as well as sub-Poissonian pumping with different strengths of correlation between the pump atoms and different correlation decay times may be studied quantitatively. The level-selective statistics of the atoms leaving the cavity is investigated as well as the photon statistics of the cavity field. Moreover, the relation to the other models used in the literature for describing the micromaser pump statistics is discussed. It is found that for sub- (super-)Poissonian pumping, the stationary expectation value of the cavity photon number (which corresponds to its time-averaged value) is larger (smaller) than the conditioned mean photon number that would result from averaging over the number of photons present in the cavity at the time instants immediately before the injection of the individual pump atoms. For Poissonian pumping, both quantities are shown to be equal. The relative standard deviation of the stationary cavity photon number is decreased (increased) for sub- (super-) Poissonian pumping, in comparison to the corresponding values that would result from Poissonian pumping. Moreover, it turns out that for sub- (super-)Poissonian pumping, the normalized coincidence probability density for the detection of the outgoing deexcited atoms is smaller (larger) than the normalized cavity field intensity correlation function at zero time delay. The difference decreases with increasing lifetime of the pump-atom correlations. Finally, the level-selective delayed coincidence probability densities of the outgoing atoms and their waiting-time distributions are found to be affected greatly by the correlation strength as well as the correlation decay time of the incoming pump atoms.

Ulrike Herzog, János A. Bergou

We investigate the effect of non-Poissonian pump fluctuations on the micromaser dynamics. Non-Poissonian micromaser pumping has been described by two, seemingly unrelated, theoretical approaches. The first employs a discrete pumping process where the pump atoms are allowed to arrive, with certain probability p, only at regularly spaced instants of time, whereas the second refers to continuously distributed arrival times of the pump atoms. Based on a generalization of the latter, we present a unified approach that can handle both situations on an equal footing. We find that for any kind of non-Poissonian pumping the resulting dynamics of the micromaser field is a non-Markovian one. For a micromaser with discrete non-Poissonian pumping, we show the equivalence of ensemble averaging and time averaging, providing a rare example where the validity of the ergodic hypothesis can be explicitly demonstrated. Moreover, we investigate the time-delayed field-field correlation function and a generalized k-photon spectrum of the cavity field, which for k=1 corresponds to the usual power spectrum. For the case that the micromaser is operated under the k-photon trapping condition, we derive exact analytical expressions for the k-photon spectrum and the corresponding correlation functions that result from the exact solution of a non-Markovian evolution problem. Provided that p>1/2, the spectrum is found to be split into several equidistant peaks for certain values of the interaction parameters. \textcopyright{} 1996 The American Physical Society.